Research On Leaching Mechanism Of Heavy Metals In Refuse Derived Fuel Combustion Fly Ash

With the development of waste incineration in China,Refuse Derived Fuel(RDF)has been widely concerned in the country because of its full combustion,high calorific value and low pollution of combustion products.The fly ash generated after the incineration of RDF has the potential of resource utilization,but it is also harmful to the environment,if it is disposed improperly.At present,there are a lot of research on the physical and chemical properties of RDF fly ash at home and abroad.However,there is little research on the leaching mechanism of heavy metals in RDF incineration fly ash.The purpose of this paper is to study the leaching mechanism of heavy metals in RDF fly ash accumulated in landfill,and to provide reference for RDF fly ash resource utilization.Focusing on the following aspects of research work:(1)In this paper,two kinds of aged fly ash(accumulation time of six months)and two kinds of fresh fly ash(accumulation time one week)were collected from different landfill sites.The leaching experiments at different pH values were carried out.The result showed that the leaching behavior of Cu,Zn,Cd,Cr and Pb in the two kinds of RDF fly ash is similar to that of cation leaching pattern.The leaching concentration decreased with the increase of pH value.The leaching behavior of Cr is also similar to the amphoteric leaching pattern,the leaching concentration of the element is the lowest at neutral pH(pH=7)and increases in acidic and alkaline environments.(2)The leaching process of heavy metals at different pH values and room temperature was simulated by geochemical simulation software.It is found that the leaching control mechanism of heavy metal elements is the same in the two kinds of fly ash.In the leaching process,Cr,Pb and Cu belong to the redox reaction sensitive elements;Cd and zinc belong to low sensitivity or no redox sensitive elements.And Cr is present in Cr(III)form;Cu is present in Cu(?)form;Cd is present in Cd(II)form;Pb is present in Pb(?)form;and Zn is present in Zn(?)form.(3)The leaching process of heavy metals at different pH values and different temperatures was simulated by geochemical simulation software.So as to study whether the temperature has an effect on the leaching behavior of heavy metals.The leaching mechanism of heavy metal elements based on pH value at different temperatures showed that the effect of temperature on the leaching of heavy metals Cd,Pb and Zn is very little,but the leaching of Cr and Cu has some influence.It can be summarized as follows:the higher of the temperature,the easier of the leaching of heavy metal elements of Cr and Cu,the lower of the temperature,the harder of the leaching of heavy metal elements of Cr and Cu.In this paper,the mechanism of heavy metal leaching in RDF combustion fly ash was studied.The influence of different temperature on the leaching behavior of heavy metals was simulated and analyzed,which had some reference value for the utilization of RDF combustion fly ash.